Forbidden Knowledge - p. 3 Dragon Age II Guide
Last update: 11 May 2016
Step 6: Finding the Grimoire of Evil
If you fulfilled the requirements mentioned above, the quest will be updated and you will learn you have to find Grimoire of Evil. Start with choosing a travel to localization from the map of the world [Anthill] #1. Here head towards north-west part of the area and find a passage (M23, 15) leading to localization [Anthill - Forgotten Bed] #2 (M67, 1).
While exploring the localization, you may come across many trapped which will be very difficult to deactivate so it is worth having a rogue in your team. The first trap is situated near the starting point and if you not deactivate it, poisonous mist will appear in the area #1. Use the switch and start attacking stone golem, who will run from the north #2. Notice that the poisonous mist will disappear if you eliminate the monster.
Now move east. In the new room you will have to eliminate a group of corpses as well as archers' skeletons #1, which shouldn't be difficult. Now carefully move east, coming across complicated and master traps #2. If you don't know how to deactivate them, try to avoid them or step up after they are activated.
In the eastern corridor you will have to eliminate new monsters and the most important matter is to eliminate secret nightmare #1. After eliminating it, deal with new corpses and archers' skeletons. Continue going east #2 and then turn north.
Be careful because there are many traps in the area and if you activate them, you will have to fight a new secret nightmare in the poisonous mist #1, which will make the fight even more difficult. After winning the fight, go to the northern room and come up to Filthy Grimoire #2 (M67, 2).
Game will give you three option, just as it did with the sinister books #1, so you can destroy grimoire, read it (Bigger Book of Mortal Coat; two bonus attribute points) or take it without reading (The Book of Forbidden Knowledge). No matter which option you choose, you will have to take part in a very difficult fight #2.
It is worth starting the fight by attacking demon Xebenkeck #1, because, just as in the case of demons of desire, it is able to influence other creatures in the room. After eliminating the monster take care of other beasts lurking in the area. First it is advisable to eliminate the filthy ones #2.
After eliminating all filthy ones, start attacking Rage Demons #1. During the fight you have to mind the health bars of your teammates and attack monsters one by one. Soon the second group of monsters will join the battle and in this case it is crucial to eliminate the living dead #2.
When the living dead is eliminated, start attacking "weaker" monsters, first the filthy ones and then the new Rage Demons #1. After the fights, look around the area because there are many interesting things, among other things the stick of Greediness, which can be found by the body of demon Xebenkeck, as well as two piles of treasures (M67, 3) situated in the corners of the room #2.